Effect of process parameters in the thermomechanical densification of pinus elliottii and eucalyptus grandis fast-growing wood

Densification parameters were investigated for the fast-growing pine and eucalyptus. Both woods showed optimal results in terms of apparent density and mechanical properties when milder treatments of 150\ub0C were applied. Pine showed mass loss and improved mechanical properties with a longer heating time of 60 min, while eucalypt performed better with shorter treatments of 30 min. Eucalypt has more highly acetylated hemicelluloses, minly composed of xylose units, which degrade more quickly with consequent decrease in mass and mechanical properties. However, apparent densities close to 1.0 g.cm-3 were obtained, and greatly enhanced bending properties, hardness, and impact resistance were observed,especially when the optimal parameters were used. Treatments at 170\ub0C or greater, while resulting in well-densified specimens, yielded inferior mechanical properties. The densified woods also presented initial apparent contact angles greater than 85\ub0, highlighting a considerable increase of hydrophobicity. The densification process therefore allows these less valuable timber species to be used in applications such as flooring and decking

Estudo de algumas propriedades mecânicas da madeira de um híbrido clonal de Eucalyptus urophylla X Eucalyptus grandis Study of some mechanical properties of wood in a clonal hybrid of Eucalyptus urophylla X Eucalyptus grandis

A procura por madeiras oriundas de reflorestamentos destinadas à serraria é uma realidade já há muitos anos, principalmente aquelas das espécies do gênero Eucalyptus. Visando buscar novas informações importantes para esse mercado, este trabalho objetivou determinar algumas propriedades mecânicas da madeira de um híbrido clonal de Eucalyptus urophylla x Eucalyptus grandis de duas idades e provenientes de talhadia simples e de reforma. Os resultados indicaram que a madeira desse híbrido apresenta boas características tecnológicas, destacando-se a segunda tora (a partir de 3 m) com as melhores propriedades de flexão estática (Módulo de Elasticidade - MOE e Módulo de Ruptura - MOR) e Compressão Axial das fibras. As árvores de maior idade (166 meses) e que sofreram dois desbastes apresentaram as melhores propriedades de flexão estática e compressão axial.<br>The search for wood originated from reforestations destined to sawmill has been observed for many years, mainly for the Eucalyptus species. Searching for information to assist this market, the aim of this study was to determine some mechanical properties of the wood from a Eucalyptus urophylla x Eucalyptus grandis clonal hybrid, at two different ages and coming from coppice and reform. The results show that the wood of this clonal hybrid presents good technological characteristics and is the second best log (starting from 3,0 m), as to static bending properties (Module of Elasticity - MOE and Module of Rupture - MOR). The oldest trees (166 months - E2) which suffered two thinning presented the best results for the property of static bending and axial crushing (CA)